Apparatus for testing concentricity of spark plug porcelains



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CELAINS 2 Sheets-Shea?| l APPARATUS FOR TESTING CONCENTRICITY OF SPARK PLUG POR Nav. 12, 1940.

, mvEN-ron CLEVELAND C. SoPER' ATTCRNEYS C. C. SOPER Nav. l2, 1940.

APPARATUS FOR TESTING vCONCENTRICITY 0F SPARK PLUG PORCELAINS 2 Sheets-Sheet 2 Filed Sept. 24, 1938 INVENTOR ELEVE/.mvo C. .SQPER ATTORN EY5 f Often,

Patented Nov. 12, 1940 UNITED STATES APPARATUS FOR TESTING CONCENTRIC'ITY 0F SPARK PLUG PORCELAINS Cleveland C. Super,

Firestone Tire & Rubber Company,

Kent,l Ohio, assgnor to The Akron,

Ohio, a, corporation of Ohio Application september 24, 193s, serial No. 231,551

5 Claims.

This invention relates to concentricity testing, more especially to apparatus for testing the concentricity of porcelains in an assembled spark plug.

when spark plugs are assembled, the porcelain insulatingthe center electrode from the metal shell of the spark plug is not of the exact shape desired. This results in the porcelain positioning the center electrode eccentrically in the metal shell and when this condition exists, the insulating quality of the porcelain is reduced. Also, mounting the porcelain eccentrically frequently acts to strain portions of the porcelain so that they are easily cracked and their eiective life shortened.

The main object of this invention is to provide apparatus for rapidly and inexpensively testing Vtheooncentricity of porcelaine in spark plugs.

Other objects of the invention are to provide accurate; easily operated and adjustable apparatus for testing varying-sized spark plugs.

The foregoing and other objects will be manifest from the following specification.

The present invention, broadly speaking, com-V' prises mounting an electric light bulb in a closed chamber and insertingr the base'of an assembled spark plug into the chamber so that light from the electric bulb is directed upon the lower end thereof. Therlthe image of the base/of the spark plug isv directed onto suitable reflecting means which project the image onto a translucent plate. This plate is provided with centering lines thereon which are designed to coincide with the image of the spark plug when the porcelain of the tested spark plug is concentrically positioned therein. The translucent plate and light directing and reecting means are all adjustably positioned so that varying sized spark plugs can be tested, the apparatus being set by inserting an assembled spark plug having a concentrically positioned porcelain in the apparatus and bringing its image into register with the lines on the centering plate.

The invention is described with reference to the accompanying drawings, of which;

Figure l 'is a vertical. section of apparatus embodying the invention; and

Figures 2 and 3 are sections taken on 2-2 and,3-3, respectively, of Figure 1.

A rectangular box, or chamber Ill is shown in Figure l enclosing the tion. This box'is hinged at II .in order 'to give ready access to its interior. A seat, or socket I2, for the base of a spark plug is detachably secured in one wall of the box l0 so that it can be lines apparatus of the invenchangedwith the varying sized spark plugs tested. A spark plug I3 having a porcelain I4, center electrode I5, ground electrode I,5a, and metal shell .I6 is shown carried by socket I2.

In order to illuminate the base of the spark 5 plug on the socket I2, two electric light bulbs I1 are mounted in the chamber lll. These bulbs are provided with substantially point-size laments I8 which are in a horizontal plane with the center of spark plug I3, thus facilitating ill0 luminating the bottoni of the spark plug. Figure 2 shows that the bulbs I1 are spaced a slight distance from the axis of the spark plug I3, as well as being positioned an appreciable distance from the spark plug. Focusing lenses I9 may be 15 mounted between the bulbs I1 and the mounted spark plug in order to concentrate light upon the end of the porcelain I4. These lenses IB are carried in tubular seats 2l which engage with threaded brackets 22 so that the position of the 20 lenses I9 relative to the spark plug I3v can be varied.

A mirror 23 is provided to reflect an image of the base of the mounted spark plug upon a downwardly 'slanted translucent plate 24 which 25 has centering lines, such as concentric circles 20a, 20h, and 20c, formed thereon. The images of the porcelain and shell of the spark plug coincide with the centering circles 20a, 2Gb, and 20c when the porcelain I4 is concentric relative to 30 the metal shell I6. In some instances, a centering, or standardization line (circle 20c) for the porcelain I4 is the only centering means required. An enlarging lens 25, which is carried by bracket 26 that is slidably received between bars 35 21, which are secured to a platform 30 on the base of the boxl, preferably is positioned between the mirror 23 and the spark plug I3. Springs 28 are secured to the bracket 2li to urge the bracket towards the spark plug I3 while a 40 screw 29 bears upon the plate 26 to limit its movement towards the spark plug. Thus, means are provided to vary the position of the enlarging lens 25 in order that the image can b-e properly focused on the plate 24. A hole 3| is formed 45 in the wall of the chamber ID so that means can be inserted into the box to vary the position of the screw 29 and thereby that of the lens 25. The mirror 23 is mounted for pivotal vertical movement within the box Ill by hinges 23a and 50 its position is controlled .by a screw 32 on which the mirror bears due to a spring 33 that is secured between the lower edge of the mirror and a pin 30a on the box I0. Hole 34 in the box Il) permits adjustment of the screw 32. 55

f Preferably the position of the translucent plate 24, usually made from glass, relative to the mirror 23 is variable. Thus. the plate is carried by a box-like member 35 that is slidably received in a rearwardly and downwardly extending opentopped compartment 36 determined by the partions 36ain the box I0. Screws 31. carried on the member 35, extend through slots 38 in the box I0 and carry wing nuts 31a so that the member 35 can be moved along the axis of the compartment 36 and be held in adjusted position by wing nuts 31a against the outer walls of the box.

Lugs 39 on opposite sides of a frame 4I which is secured in the member 35 by screws 43 engage the lower surface of the sides of the plate 24 to form a support therefor. The frame 4| engages the upper edge of the plate while the lower edge thereof bears upon a substantially vertically extending stop plate 44 which is carried by a cover member 45. 'I'he cover member 45 is hinged at 46 to a downwardly and rearwardly extending plate 4l associated with the upper portion of the front of the box Ill, the cover member being retained .in position by means hereinafter described.

Sometimes it is most convenient to change the glass plate for a diiferent sized spark plug. Thus the upper 30 portion of the box Il) may be raised whereby the plate 44 are accessible extend down sufciently to overlap the partitions 48 and prevent Apassage of light to the plate 24 G5 by an undesired route. The cover 5 2 engages with stop plate 44 through slotted ears 55 formed on the cover member 45. Screws 56, the cover 52, bear upon the ears 55 to retain the stop plate in position while it is freed for [o downward movement by loosening the screws A fan 51 is mounted Within the box I0 to circulate air therethrough' since the bulbs l1 generate appreciable heat within the box. Apertures '5 58. Which may be screened, are provided in several extends downwardly portions of the box I 0 tion.

In operation, it is seen that a spark plug is positioned upon the socket I2 and light from the bulbs Il focused upon the bottom of the mounted spark plug. An image of the end of the spark plug is projected upon the mirror 23 by the lens 25, the mirror reflecting the image onto the translucent plate 24. Then the operator of the apparatus has a direct view of the plate 24 through the compartment 36 whereby he can directly and rapidly compare the projected image with the theoretical, or desired, image formed upon .the translucent plate 24.

From the foregoing description, it will be observed that a rapid. concentricity testing apparatus for assembled spark plugs has been provided.

In accordance with the patent statutes, I have described the construction and operation of an embodiment of the invention. However, be understood that various modiiications can be made without departing from the scope of the invention as defined in the appended claims.

What is claimed is:

l. Apparatus for testing the concentricity of to facilitate air circulalight therefrom onto the base of a mounted spark plug, a mirror positioned in said chamber -on the axis of said socket to catch and reflect the image of the base of a mounted spark plug, a lens adin a wall of said chamber on the forward side of said mirror to receive an image therefrom, means for controlling the position of said mirror relative to said plate and said socket whereby the position of the image reiiected onto said plate ected onto said plate can becontrolled and be compared with said standardization lines.

3. Apparatus for testing the concentricity of ssembled spark plugs having porcelains visible 'om the lower end thereof, said apparatus comrisng a closed chamber, illuminating means lounted in said chamber, a socket for mounting :le lower end of a spark plug secured in a wall E said chamber to expose the lower portion of a iounted spark plug to the interior of said chamer, a lens positioned in said chamber between aid socket and said illuminating means for ocusing light therefrom onto the base of a mounted spark plug, 'a mirror positioned in said :h'amber on the axis of said socket to catch and 'eflect the image of the base of a mounted spark `nlug, and atranslucent plate having standardizaiion lines thereon mounted in a wall of said chamber on the forward side of said mirror to receive an image therefrom whereby the position of the image reflected onto said plate can be compared with said standardization lines.

4.' Apparatus for testing the concentricity of assembled spark plugs having porcelains visible from the lower end thereof, said apparatus comprising a closed chamber, a socket for mounting the lower end of a spark plug secured in a wall of said chamber to expose the lower portion of a mounted spark plug to the interior of said chamber, means in said chamber for illuminating the base of a mounted spark plug, a mirror positioned in said chamber to catch and reect the image of the base of a mounted spark plug, and a translucent plate having standardization lines thereon mounted in a wall of said chamber on the forward side of said mirror to receive an image therefrom whereby the position of the reflected image can be compared with said standardization lines.

5. Apparatus for testing the concentricity of an assembled spark plug having an electrode, a porcelain and a shell visible from the lower end thereof, said apparatus comprising a closed chamber, means for mounting the lower end of a spark plug associated with a wall of said cham- Iber to expose the lower portion of a mounted spark plug to the interior of said chamber, illuminating means in said chamber adjacent said mounting means but in spaced relation to the axis thereof for illuminating the base of a mounted spark plug, image transmitting means positioned in said chamber, and a translucent plate adapted to receive the image of the base of a mounted spark plug, said translucent plate having a plurality of concentric circles formed thereon with which the image of the electrode, porcelain and shell coincides when spark plug is concentrically positioned in the metal shell.

CLEVELAND C. SOPER.

the porcelain of the mounted 

